Relay device and relay system

ABSTRACT

An LP table retains a combination of a physical port and a VLAN identifier in association with a logical port. When a frame is received at the physical port, a table processing unit acquires a logical port based on the LP table. An FDB processing unit learns a source MAC address contained in the received frame in association with the logical port acquired by the table processing unit to an FDB. A plurality of logical ports are set for the physical port by the LP table. A loop prevention unit prohibits frame relay between the plurality of logical ports set for the physical port.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2015-191551 filed on Sep. 29, 2015, the content of which is herebyincorporated by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a relay device and a relay system, forexample, a relay system made up of a full-mesh network and a relaydevice used in the relay system.

BACKGROUND OF THE INVENTION

For example, Japanese Patent Application Laid-Open Publication No.2008-193614 (Patent Document 1) describes a method in which VLAN-IDs aremanaged by dividing them into sub-group IDs and sub-IDs includedtherein. In this method, ports to which the same sub-group ID isallocated belong to the same flooding domain, but whether relay betweenthe ports therein is possible is determined based on the sub-IDs.

SUMMARY OF THE INVENTION

For example, a full-mesh network in which relay devices are connected ina full mesh has been known as one of network topologies. When threerelay devices are provided, for example, each of the three relay devicesis connected to the remaining two relay devices through respectivelydifferent physical ports and communication lines.

In such a network, for example, an advantage that one hop relay ispossible between the respective relay devices can be obtained, but thereare mainly two concerns in the construction of the network. The firstconcern is that the cost may increase due to the increase in the numberof required physical ports and communications lines. The second concernis that a loop path may be created when relaying, for example, amulticast frame.

The present invention has been made in view of such problems, and anobject thereof is to provide a relay device and a relay system capableof constructing a full-mesh network at low cost.

The above and other objects and novel characteristics of the presentinvention will be apparent from the description of the presentspecification and the accompanying drawings.

The following is a brief description of an outline of the representativeembodiment of the invention disclosed in the present application.

A relay device according to an embodiment includes: a physical port; alogical port table; a table processing unit; an FDB; an FDB processingunit; and a loop prevention unit. The logical port table retains acombination of the physical port and a VLAN identifier in associationwith a logical port. The table processing unit acquires the logical portbased on the logical port table when a frame is received at the physicalport. The FDB processing unit learns a source MAC address contained inthe received frame in association with the logical port acquired by thetable processing unit to the FDB. Here, a plurality of the logical portsare set for the physical port by the logical port table. The loopprevention unit prohibits frame relay between the plurality of logicalports set for the physical port.

The advantages obtained by the representative embodiment of theinvention disclosed in the present application will be briefly describedas follows. That is, it is possible to construct a full-mesh network atlow cost in a relay device and a relay system.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration example ofmain components in a relay system according to the first embodiment ofthe present invention;

FIG. 2 is a block diagram illustrating a schematic configuration exampleof main components in the relay device of FIG. 1;

FIG. 3A is a schematic diagram illustrating a configuration example of alogical port table of FIG. 2;

FIG. 3B is a schematic diagram illustrating a configuration example of aVID conversion table of FIG. 2;

FIG. 3C is a schematic diagram illustrating a configuration example ofan FDB of FIG. 2;

FIG. 3D is a schematic diagram illustrating a configuration example of amulticast table of FIG. 2;

FIG. 4 is a flowchart illustrating an example of process contents of aloop prevention unit of FIG. 2;

FIG. 5 is an explanatory diagram illustrating a schematic operationexample of the relay system of FIG. 1;

FIG. 6 is an explanatory diagram illustrating an operation example to bea comparative example of FIG. 5;

FIG. 7 is an explanatory diagram illustrating another operation exampleto be a comparative example of FIG. 5;

FIG. 8 is a block diagram illustrating a configuration example of maincomponents in a relay device according to the second embodiment of thepresent invention;

FIG. 9 is a block diagram illustrating a configuration example of ahigh-bandwidth line card in the relay device of FIG. 8;

FIG. 10A is a schematic diagram illustrating a configuration example ofan LC table of FIG. 9;

FIG. 10B is a schematic diagram illustrating a configuration example ofa port table of FIG. 9;

FIG. 10C is a schematic diagram illustrating a configuration example ofan FDB of FIG. 9;

FIG. 11 is an explanatory diagram illustrating a schematic operationexample in the case where the relay device of FIG. 8 is applied to therelay system of FIG. 5;

FIG. 12 is an explanatory diagram illustrating another schematicoperation example in the case where the relay device of FIG. 8 isapplied to the relay system of FIG. 5;

FIG. 13A is a block diagram illustrating a schematic configurationexample of main components relating to a logical port in the relaydevice according to the first embodiment of the present invention;

FIG. 13B is a schematic diagram illustrating a configuration example ofa logical port table of FIG. 13A;

FIG. 13C is a schematic diagram illustrating a configuration example ofan FDB of FIG. 13A;

FIG. 14A is a block diagram illustrating a schematic configurationexample of main components of a relay device to be a comparative exampleof FIG. 13A; and

FIG. 14B is a schematic diagram illustrating a configuration example ofan FDB of FIG. 14A.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

In the embodiments described below, the invention will be described in aplurality of sections or embodiments when required as a matter ofconvenience. However, these sections or embodiments are not irrelevantto each other unless otherwise stated, and the one relates to the entireor a part of the other as a modification example, details, or asupplementary explanation thereof. Also, in the embodiments describedbelow, when referring to the number of elements (including number ofpieces, values, amount, range, and the like), the number of the elementsis not limited to a specific number unless otherwise stated or exceptthe case where the number is apparently limited to a specific number inprinciple, and the number larger or smaller than the specified number isalso applicable.

Further, in the embodiments described below, it goes without saying thatthe components (including element steps) are not always indispensableunless otherwise stated or except the case where the components areapparently indispensable in principle. Similarly, in the embodimentsdescribed below, when the shape of the components, positional relationthereof, and the like are mentioned, the substantially approximate andsimilar shapes and the like are included therein unless otherwise statedor except the case where it is conceivable that they are apparentlyexcluded in principle. The same goes for the numerical value and therange described above.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that componentshaving the same function are denoted by the same reference charactersthroughout the drawings for describing the embodiments, and therepetitive description thereof will be omitted.

First Embodiment

<<Logical Port Function>>

The relay device according to the first embodiment is assumed to have afunction referred to as a logical port. First, a concept of the logicalport and a basic configuration for realizing the logical port will bedescribed. FIG. 13A is a block diagram illustrating a schematicconfiguration example of main components relating to a logical port inthe relay device according to the first embodiment of the presentinvention, FIG. 13B is a schematic diagram illustrating a configurationexample of a logical port table of FIG. 13A, and FIG. 13C is a schematicdiagram illustrating a configuration example of an FDB of FIG. 13A. FIG.14A is a block diagram illustrating a schematic configuration example ofmain components of a relay device to be a comparative example of FIG.13A, and FIG. 14B is a schematic diagram illustrating a configurationexample of an FDB of FIG. 14A.

First, a relay device SW′ of the comparative example illustrated in FIG.14A includes a plurality of physical ports PP1, PP2, . . . , and a frameprocessing unit 15′. The frame processing unit 15′ includes an FDB(Forwarding DataBase) and an FDB processing unit 18 which performslearning and retrieval of the FDB. In the example of FIG. 14A, terminalsTM1 and TM2 are present ahead of a communication line 10 a connected tothe physical port PP1 and a terminal TM3 is present ahead of acommunication line 10 b connected to the physical port PP2. Theterminals TM1, TM2 and TM3 have the MAC addresses “MA1”, “MA2” and“MA3”, respectively, and VLAN identifiers “VID1”, “VID2” and “VID3” arerespectively allocated thereto.

In this case, as illustrated in FIG. 14B, a port identifier {PP1} islearned in association with “MA1” and “VID1” to the FDB. The portidentifier {PP1} indicates the identifier (ID) of the physical port PP1,and for example, {AA} is supposed to indicate the identifier of “AA” inthe same manner in the present specification. Further, the portidentifier {PP1} is learned in association with “MA2” and “VID2” and aport identifier {PP2} is learned in association with “MA3” and “VID3” tothe FDB of FIG. 14B.

A relay device SW illustrated in FIG. 13A realizes a configurationequivalent to the relay device SW′ of FIG. 14A by the logical portfunction. Though not particularly limited, the relay device SWillustrated in FIG. 14A is a layer 2 (L2) switch or the like forperforming an L2 processing of an OSI reference model, and includes aphysical port PPh1 and a frame processing unit 15. The frame processingunit 15 includes a logical port table (hereinafter, abbreviated as LPtable below) 21, a table processing unit 16 for performing processingbased on the LP table, an FDB, and the FDB processing unit 18 forperforming learning and retrieval of the FDB.

In the example of FIG. 13A, unlike the case of FIG. 14A, the terminalsTM1, TM2 and TM3 similar to those in FIG. 14A are present ahead of acommunication line 10 connected to the physical port PPh1. In this case,the LP table 21 previously retains combinations of the one physical portPPh1 and one or a plurality of VLAN identifiers in association with onelogical port based on the user setting as illustrated in FIG. 13B.Specifically, the LP table 21 retains a combination of the portidentifier {PPh1} and the VLAN identifiers “VID1” and “VID2” inassociation with the logical port LP1 (port identifier {LP1}), andretains a combination of the port identifier {PPh1} and the VLANidentifier “VID3” in association with the logical port LP2 (portidentifier {LP2}).

The logical port LP is a port equivalent to the physical port PP1 ofFIG. 14A, and the logical port LP2 is a port equivalent to the physicalport PP2 of FIG. 14A. In this way, the logical ports provide a mechanismfor virtually mounting a plurality of physical ports on the one physicalport PPh1. If there are ten physical ports and a bandwidth of eachphysical port is 10 Gbps in FIG. 14A, this configuration can be replacedwith the configuration of FIG. 13A by, for example, providing thephysical port PPh1 having a bandwidth of 100 Gbps and then providing tenlogical ports on the physical port.

When a frame is received at the physical port PPh1, the table processingunit 16 acquires the logical port based on the LP table 21. The FDBprocessing unit 18 learns a source MAC address contained in the frame inassociation with the logical port acquired by the table processing unit16 to the FDB. Specifically, when a frame containing the source MACaddress “MA1” and the VLAN identifier “VID1” from the terminal TM1 isreceived at the physical port PPh1, the table processing unit 16acquires the port identifier {LP1} based on the logical port table 21.The FDB processing unit 18 learns the source MAC address “MA1” inassociation with the port identifier {LP1} to the FDB as illustrated inFIG. 13C.

Similarly, when a frame from the terminal TM2 is received at thephysical port PPh1, the table processing unit 16 acquires the portidentifier {LP1}. The FDB processing unit 18 learns the source MACaddress “MA2” of the frame in association with the port identifier {LP1}to the FDB. Further, when a frame from the terminal TM3 is received atthe physical port PPh1, the table processing unit 16 acquires the portidentifier {LP2}. The FDB processing unit 18 learns the source MACaddress “MA3” of the frame in association with the port identifier {LP2}to the FDB.

Further, when a frame containing the destination MAC address “MA1” isreceived at, for example, a physical port (not illustrated), the FDBprocessing unit 18 retrieves the FDB with using “MA1” as a retrievalkey, and acquires the port identifier {LP1} to be a destination(referred to as a destination port identifier). When the destinationport identifier is the port identifier of the logical port, the tableprocessing unit 16 replaces the destination port identifier {LP1} withthe port identifier of the physical port (here, {PPh1}) based on thelogical port table 21. The frame processing unit 15 relays the receivedframe to the physical port PPh1 corresponding to the destination portidentifier {PPh1}.

Here, for example, the FDB processing unit 18 learns the MAC address“MA1” in association with the port identifier {LP1} to the FDB inresponse to the frame from the terminal TM1, but may additionally learnthe VLAN identifier “VID1”. In this case, in the destination retrievaldescribed above, the FDB processing unit 18 retrieves the FDB with using“MA1” and “VID1” as retrieval keys.

By using the logical port function described above, for example, thecost reduction can be achieved. Namely, by using the configuration ofFIG. 13A, a plurality of physical ports and a plurality of communicationlines (for example, optical fibers) which are required in theconfiguration of FIG. 14A can be replaced with one physical port and onecommunication line.

<<Configuration of Relay System>>

FIG. 1 is a schematic diagram illustrating a configuration example ofmain components in a relay system according to the first embodiment ofthe present invention. The relay system illustrated in FIG. 1 includes aplurality of relay devices connected via a communication line. In FIG.1, relay devices SW1 to SW3 and SW′1 to SW′3 are, for example, L2switches and others. In addition, the relay system illustrated in FIG. 1includes a network NW in which relaying based on VLAN identifiers isperformed. Here, a backbone VLAN identifier BVID based on theIEEE802.1ah (referred to also as PBB (Provider Backbone Bridge)standard) is used as the VLAN identifier. The network NW is, forexample, a PBB-TE (Traffic Engineering) network or the like and isconfigured of relay devices and communication lines as needed.

The network NW has a configuration in which the relay devices SW1 to SW3are connected in a full mesh. Each of the relay devices SW1 to SW3includes the physical ports PPh1 and PPh2. The physical ports PPh1 ofthe relay devices SW1 to SW3 are connected to the network NW via therespective communication lines 10. Also, the physical ports PPh2 of therelay devices SW1 to SW3 are connected to the relay devices SW′1 to SW′3via the communication lines 10, respectively.

Further, the terminals TM1 to TM3 are connected to the relay devicesSW′1 to SW′ 3, respectively. The terminals TM1, TM2 and TM3 have the MACaddresses “MA1”, “MA2” and “MA3”, respectively, and “SVID1”, “SVID2” and“SVID3” based on the IEEE802.1ad are respectively allocated thereto asthe VLAN identifiers VID.

Though not particularly limited, each of the relay devices SW1 to SW3 isan edge switch which can perform the frame relay between a PB (ProviderBridge) network and the PBB (Provider Backbone Bridge) network 11. ThePB network is a network in which the service VLAN identifier SVID isused, and the PBB network 11 is a network in which the backbone VLANidentifier BVID (and service instance identifier ISID) based on theIEEE802.1ah is used. For example, the terminals TM1 to TM3 are terminalsbelonging to the same company. The relay devices SW1 to SW3 are set atrespectively different locations in the same company and thecommunication among these locations is made through the PBB network 11having the relay devices SW1 to SW3 as edge switches.

Here, the logical ports described with reference to FIG. 13A and othersare set on the physical ports PPh1 and PPh2 of the relay devices SW1 toSW3. The logical ports LP1_1 and LP1_2 are set in association with thebackbone VLAN identifiers “BVID1” and “BVID2”, respectively, on thephysical port PPh1 of the relay device SW1. The logical port LP2_1 isset in association with the service VLAN identifier “SVID1” on thephysical port PPh2 of the relay device SW1.

Similarly, the logical ports LP1_1 and LP1_2 are set in association with“BVID1” and “BVID3”, respectively, on the physical port PPh1 of therelay device SW2, and the logical port LP2_1 is set in association with“SVID2” on the physical port PPh2. Further, the logical ports LP1_1 andLP1_2 are set in association with “BVID3” and “BVID2”, respectively, onthe physical port PPh1 of the relay device SW3, and the logical portLP2_1 is set in association with “SVID3” on the physical port PPh2.

When a frame containing “BVID1” from the relay device SW1 is received,the network NW relays the frame to the relay device SW2, and when aframe containing “BVID2” is received, the network NW relays the frame tothe relay device SW3. Also, when a frame containing “BVID1” from therelay device SW2 is received, the network NW relays the frame to therelay device SW1, and when a frame containing “BVID3” is received, thenetwork NW relays the frame to the relay device SW3. Further, when aframe containing “BVID3” from the relay device SW3 is received, thenetwork NW relays the frame to the relay device SW2, and when a framecontaining “BVID2” is received, the network NW relays the frame to therelay device SW1.

With the VLAN configuration described above, the relay system of FIG. 1has the configuration in which the relay devices SW1 to SW3 areconnected in a full mesh, and the physical ports PPh1 (logical ports setthereon) of the relay devices SW1 to SW3 serve as the ports connected tothe full-mesh network. Namely, the relay devices SW and SW2 areconnected through the logical ports LP1_1 thereof and the relay devicesSW1 and SW3 are connected through the logical ports LP1_2 thereof. Also,the relay devices SW2 and SW3 are connected through the logical portLP1_2 of the relay device SW2 and the logical port LP1_1 of the relaydevice SW3.

As described above, by using the logical ports LP1_1 and LP1_2, forexample, the relay device SW1 and the network NW can be connected by onephysical port PPh1 and one communication line 10 instead of a pluralityof (for example, two) physical ports and a plurality of (for example,two) communication lines. The same is true for the relay devices SW2 andSW3. As a result, the full-mesh network can be constructed at low cost.Note that the full-mesh network is configured of the three relay devicesSW1 to SW3 in this example, but if the network is configured of morerelay devices, this effect becomes greater.

<<Configuration of Relay Device>>

FIG. 2 is a block diagram illustrating a schematic configuration exampleof main components in the relay device of FIG. 1. FIG. 3A is a schematicdiagram illustrating a configuration example of a logical port table ofFIG. 2, FIG. 3B is a schematic diagram illustrating a configurationexample of a VID conversion table of FIG. 2, FIG. 3C is a schematicdiagram illustrating a configuration example of an FDB of FIG. 2, andFIG. 3D is a schematic diagram illustrating a configuration example of amulticast table of FIG. 2.

FIG. 2 illustrates a schematic configuration example of the relaydevices SW1 to SW3 of FIG. 1. FIGS. 3A to 3D illustrate a configurationexample of each table provided in the relay device SW1 of FIG. 1. Therelay device SW of FIG. 2 includes two physical ports PPh1 and PPh2 andthe frame processing unit 15. The frame processing unit 15 includes aVID conversion unit 17, a multicast (hereinafter, abbreviated as MC)processing unit 19 and a loop prevention unit 20 in addition to the LPtable 21, the table processing unit 16, the FDB and the FDB processingunit 18 illustrated in FIG. 13A.

The LP table 21 retains the combination of the physical port and theVLAN identifier VID in association with the logical port based on theuser setting or the like as illustrated in FIG. 3A. For example, theport identifier {LP1_1} is retained in association with the portidentifier {PPh1} and “BVID1”, and the port identifier {LP1_2} isretained in association with the port identifier {PPh1} and “BVID2”. Inaddition, the port identifier {LP2_1} is retained in association withthe port identifier {PPh2} and “SVID1”. When a frame is received at aphysical port, the table processing unit 16 acquires the logical portbased on the LP table 21 as described above.

The VID conversion unit 17 includes a VID conversion table 22. The VIDconversion table 22 retains the service VLAN identifier SVID inassociation with an internal VLAN identifier IVID in advance based onthe user setting as illustrated in FIG. 3B. Also, the VID conversiontable 22 retains the backbone VLAN identifier BVID and the serviceinstance identifier ISID in association with an internal VLAN identifierIVID.

In the example of FIG. 3B, “SVID1” of the PB network, “BVID1” and“ISID1”, and “BVID2” and “ISID1” of the PBB network 11 of FIG. 1 arerespectively associated with “IVID1”. Namely, in this example, theterminals TM1 to TM3 belonging to the same company are set to the sameflooding domain by “IVID1”, and each of the locations is distinguishedby “BVID1” and “BVID2”.

The VID conversion unit 17 converts a predetermined VLAN identifier(SVID, or BVID and ISID) contained in the received frame into aninternal VLAN identifier IVID based on the VID conversion table 22 bythe user setting. Also, the VID conversion unit 17 converts an internalVLAN identifier IVID contained in the frame to be transmitted into apredetermined VLAN identifier.

In the learning of the FDB, as described with reference to FIG. 13C, theFDB processing unit 18 learns the source MAC address contained in thereceived frame in association with the logical port acquired by thetable processing unit 16 to the FDB. Further, in this case, the FDBprocessing unit 18 retains the source MAC address in association withthe internal VLAN identifier IVID converted by the VID conversion unit17 in addition to the logical port to the FDB as illustrated in FIG. 3C.Meanwhile, in the destination retrieval of FDB, the FDB processing unit18 retrieves the FDB with using the destination MAC address and theinternal VLAN identifier IVID contained in the received frame asretrieval keys, thereby acquiring the destination port identifier.

For example, when a frame from the terminal TM1 is received at thelogical port LP2_1, the FDB processing unit 18 of the relay device SW1of FIG. 1 learns “MA1” and “IVID1” in association with the portidentifier {LP2_1} to the FDB. Also, when a frame from the terminal TM2is received at the logical port LP1_1, the FDB processing unit 18 learns“MA2” and “IVID1” in association with the port identifier {LP1_1} to theFDB. Further, when a frame from the terminal TM3 is received at thelogical port LP1_2, the FDB processing unit 18 learns “MA3” and “IVID1”in association with the port identifier {LP1_2} to the FDB.

The MC processing unit 19 includes an MC table 23. The MC table 23retains a correspondence relation between the internal VLAN identifierIVID and one or a plurality of logical ports in advance based on theuser setting as illustrated in FIG. 3D. In the example of FIG. 3D, thecorrespondence relation between “IVID1” and the port identifiers{LP1_1}, {LP1_2} and {LP2_1} is retained. When the received frame is amulticast frame or when the result of the destination retrieval of theFDB is mishit, the MC processing unit 19 determines one or a pluralityof logical ports to be a destination with reference to the MC table 23by the use of the internal VLAN identifier IVID of the frame.

The loop prevention unit 20 prohibits the frame relay between aplurality of logical ports (for example, LP1_1 and LP1_2) set on thephysical port (for example, PPh1) based on the user setting or the like.At this time, the user can determine whether to prohibit the relaybetween the logical ports (that is, whether to enable the loopprevention unit 20) for each of the physical ports (for example, PPh1and PPh2) on which the logical port is to be set.

FIG. 4 is a flowchart illustrating an example of process contents of theloop prevention unit of FIG. 2. In FIG. 4, when a frame to betransmitted (that is, egress frame) is received (step S101), the loopprevention unit 20 determines whether there is a physical port to whichthe prohibition of the relay between logical ports is set by the user(step S102). When there is the physical port, the loop prevention unit20 determines whether the relay of the received frame is the frame relaybetween the logical ports set on the physical port (step S103).

For example, when the prohibition of the relay between the logical portsis set to the physical port PPh1, the loop prevention unit 20 extractsthe frame which has been received at a logical port LP1_x (x is anarbitrary integer) and whose destination port is the logical port LP1_y(y is an arbitrary integer other than x). Then, the loop prevention unit20 discards the extracted frame (step S104). Note that the frame whichhas been received at the logical port LP1_x and whose destination portis the logical port LP1_x is discarded by the return prohibitingfunction generally provided in the relay device. The loop preventionunit 20 does nothing when the respective conditions of the steps S101 toS103 are not satisfied, and ends the process.

<<Operation of Relay System>>

FIG. 5 is an explanatory diagram illustrating a schematic operationexample of the relay system of FIG. 1. FIG. 6 and FIG. 7 are explanatorydiagrams each illustrating an operation example to be a comparativeexample of FIG. 5. The case where the terminal TM1 transmits a multicastframe MCFn1 to all the terminals in the company including the terminalsTM2 and TM3 is assumed here.

First, FIG. 6 illustrates an operation example in the case where adirect communication path between the relay device SW1 and the relaydevice SW3 is not provided in the network NW′ unlike the relay system ofFIG. 1. Accordingly, the relay devices SW1 to SW3 constitute a tree-typenetwork 25. Also, FIG. 6 assumes the case where each of the relaydevices SW1 to SW3 is not provided with the loop prevention unit 20illustrated in FIG. 2 or the case where the loop prevention unit 20 isprovided but the prohibition of the relay between logical ports is notset.

In FIG. 6, the relay device SW1 receives the multicast frame MCFn1 fromthe terminal TM1 at the physical port PPh2. The multicast frame MCFn1contains “MA1” serving as a source MAC address (SA), a predeterminedmulticast address (hereinafter, referred to as MCA) serving as adestination MAC address (DA), and “SVID1”. The relay device SW1 receivesthe frame at the logical port LP2_1 with reference to the LP table 21 ofFIG. 3A by the use of the combination of the physical port PPh2 and“SVID1”.

Also, since the destination MAC address is MCA, the relay device SW1performs the relay based on the MC table 23. In the case of theconfiguration of FIG. 6, the MC table 23 retains the correspondencerelation between “IVID1” and the port identifiers {LP1_1} and {LP2_1}unlike the case of FIG. 3D. Based on this, the relay device SW1 relaysthe multicast frame MCFn1 to the logical port LP1_1 except the logicalport LP2_1 which has received the frame. At this time, the relay deviceSW1 adds “BVID1” as the VLAN identifier to the frame based on the LPtable 21.

The network NW′ relays the multicast frame MCFn1 to the relay device SW2based on “BVID1”, and the relay device SW2 receives the frame at thephysical port PPh1. The relay device SW2 receives the frame at thelogical port LP1_1 with reference to its own LP table 21 by the use ofthe combination of the physical port PPh1 and “BVID1”.

Also, since the destination MAC address is MCA, the relay device SW2performs the relay based on its own MC table 23. The MC table 23 retainsthe information similar to that of FIG. 3D, and the relay device SW2relays the multicast frame MCFn1 to the logical ports LP1_2 and LP2_1except the logical port LP1_1 which has received the frame based on theinformation. At this time, the relay device SW2 adds “SVID2” to theframe to be relayed to the logical port LP2_1 and adds “SVID3” to theframe to be relayed to the logical port LP1_2 based on its own LP table21.

The frame relayed to the logical port LP2_1 is received by the terminalTM2. Meanwhile, the frame relayed to the logical port LP1_2 is relayedto the relay device SW3 through the network NW′. The relay device SW3receives the frame at the physical port PPh1. The relay device SW3receives the frame at the logical port LP1_1 with reference to its ownLP table 21 by the use of the combination of the physical port PPh1 and“BVID3”.

Also, since the destination MAC address is MCA, the relay device SW3performs the relay based on its own MC table 23. The MC table 23 retainsthe correspondence relation between “IVID1” and the port identifiers{LP1_1} and {LP2_1} like the case of the relay device SW1. The relaydevice SW3 relays the multicast frame MCFn1 to the logical port LP2_1except the logical port LP1_1 which has received the frame based onthis. At this time, the relay device SW3 adds “SVID3” to the frame to berelayed to the logical port LP2_1 based on its own LP table 21. Theframe relayed to the logical port LP2_1 is received by the terminal TM3.

As described above, in the case of the tree-type network 25, the relaydevices SW1 to SW3 can distribute the multicast frame MCFn1 to eachlocation when the loop prevention unit 20 is not provided or when theloop prevention unit 20 is provided and the prohibition of the relaybetween logical ports is not set. However, when the full-mesh network 11is used as illustrated in FIG. 7, the infinite loop may occur unless theprohibition of relay between logical ports is set.

FIG. 7 illustrates an operation example in the case where the relaydevices SW1 to SW3 permit the relay between logical ports in thefull-mesh network 11 similar to that of FIG. 1. In FIG. 7, unlike thecase of FIG. 6, for example, the physical port PPh1 of the relay device(first relay device) SW1 is connected at least to the relay device(second relay device) SW2 and the relay device (third relay device) SW3.Further, the relay device SW2 is connected to the relay device SW3without interposing the relay device SW1.

In the following description, the difference from FIG. 6 will be mainlydescribed. In the case of FIG. 7, the relay device SW1 relays themulticast frame MCFn1 received at the logical port LP2_1 to the logicalport LP1_2 in addition to the logical port LP1_1 based on the MC table23 of FIG. 3D. Based on the LP table 21 of FIG. 3A, “BVID2” is added tothe frame relayed to the logical port LP1_2.

The network NW relays the multicast frame MCFn1 to the relay device SW3based on “BVID2”, and the relay device SW3 receives the frame at thephysical port PPh1. The relay device SW3 receives the frame at thelogical port LP1_2 with reference to its own LP table 21 by the use ofthe combination of the physical port PPh1 and “BVID2”.

Also, since the destination MAC address is MCA, the relay device SW3performs the relay based on its own MC table 23. The MC table 23 retainsinformation similar to that of FIG. 3D, and the relay device SW3 relaysthe multicast frame MCFn1 to the logical ports LP1_1 and LP2_1 exceptthe logical port LP1_2 which has received the frame based on theinformation. At this time, the relay device SW3 adds “SVID3” to theframe to be relayed to the logical port LP2_1 and adds “BVID3” to theframe to be relayed to the logical port LP1_1 based on its own LP table21.

The frame relayed to the logical port LP2_1 is received by the terminalTM3. Meanwhile, the frame relayed to the logical port LP1_1 is relayedto the relay device SW2 through the network NW. The relay device SW2receives the frame at the physical port PPh1. The relay device SW2receives the frame at the logical port LP1_2 with reference to its ownLP table 21 by the use of the combination of the physical port PPh1 and“BVID3”.

Here, since the destination MAC address is MCA, the relay device SW2relays the multicast frame MCFn1 to the logical ports LP1_1 and LP2_1based on its own MC table 23. The frame relayed to the logical portLP1_1 is received at the logical port LP1_1 of the relay device SW1, andis then relayed by the relay device SW1 to the logical port LP1_2 againin addition to the logical port LP2_1.

Also, as described with reference to FIG. 6, the relay device SW3 hasreceived the multicast frame MCFn1 from the relay device SW2 at thelogical port LP1_1, and relays the frame to the logical ports LP1_2 andLP2_1 in the configuration of FIG. 7. The frame relayed to the logicalport LP1_2 is received at the logical port LP1_2 of the relay deviceSW1, and is then relayed by the relay device SW1 to the logical portLP1_1 again in addition to the logical port LP2_1. Due to the operationdescribed above, the infinite loop may occur.

Thus, in FIG. 5, each of the relay devices SW1 to SW3 includes the loopprevention unit 20 illustrated in FIG. 2, and the loop prevention unit20 prohibits the relay between logical ports for the physical port PPh1.In this case, like the case of FIG. 6, the relay device SW2 receives themulticast frame MCFn1 transmitted from the logical port LP1_1 of therelay device SW1 at the logical port LP1_1. The relay device SW2determines the logical ports LP1_2 and LP2_1 as the destination portsbased on its own MC table 23. Since the frame relayed to the logicalport LP1_2 corresponds to the relay between logical ports set on thephysical port PPh1, the loop prevention unit 20 of the relay device SW2discards the frame.

Similarly, the relay device SW3 receives the multicast frame MCFn1transmitted from the logical port LP1_2 of the relay device SW1 at thelogical port LP1_2. The relay device SW3 determines the logical portsLP1_1 and LP2_1 as the destination ports based on its own MC table 23.Since the frame relayed to the logical port LP1_1 corresponds to therelay between logical ports set on the physical port PPh1, the loopprevention unit 20 of the relay device SW3 discards the frame.

In this manner, it is possible to construct the full-mesh network 11capable of distributing the multicast frame to the terminals TM1 to TM3while preventing the loop of the frame. Also when the one relay device(for example, SW2) prohibits the relay between logical ports in FIG. 5,the prevention of the loop is possible. In this case, however, the relaydevice SW2 duplicately receives the frame from the relay device SW1 andthe frame from the relay device SW3. Therefore, it is desirable that theloop prevention units 20 of all the relay devices SW1 to SW3 prohibitthe relay between logical ports for the physical ports PPh1 asillustrated in FIG. 5.

Namely, since one hop relay is possible between the relay devices SW1 toSW3 in the full-mesh network 11, the loop of the frame and the duplicatetransmission can be prevented by prohibiting the relay between logicalports corresponding to two or more hop relay. Note that the case wherethe full-mesh network 11 is constructed of the three relay devices SW1to SW3 has been taken as an example here, but the same is true for thecase where it is constructed of four or more relay devices. Further,with respect to the physical ports PPh2 of the relay devices SW1 to SW3in FIG. 5, whether the relay between logical ports is prohibited may beappropriately determined in accordance with the network configurationconnected to the physical ports PPh2 or the like.

As described above, by using the relay device and the relay systemaccording to the first embodiment, typically, the full-mesh network canbe constructed at low cost.

Second Embodiment

<<Detailed Configuration of Relay Device>>

FIG. 8 is a block diagram illustrating a configuration example of maincomponents in a relay device according to the second embodiment of thepresent invention. The relay device SW illustrated in FIG. 8 is achassis-type L2 switch in which a plurality of cards are mounted in onechassis. The relay device SW includes one or a plurality of (here, two)high-bandwidth line cards LCh1 and LCh2, one or a plurality of (here,one) low-bandwidth line card LC11, and a fabric path unit 30. Each ofthe line cards LCh1, LCh2 and LC11 communicates (transmits and receives)a frame with an external device. The fabric path unit 30 relays a framebetween the line cards.

Each of the high-bandwidth line cards LCh1 and LCh2 includes a physicalport PPh1 or PPh2 and a fabric terminal FP. The physical ports PPh1 andPPh2 are the ports for which the logical ports described in the firstembodiment and others are to be set. The physical ports PPh1 and PPh2are connected to, for example, the communication line 10 of 100 Gbps orthe like. Meanwhile, the low-bandwidth line card LC11 includes nphysical ports PP11 to PP1 n and a fabric terminal FP. The physicalports PP11 to PP1 n are the ports for which the logical port is not tobe set. Each of the physical ports PP11 to PP1 n is connected to, forexample, a communication line 31 of 10 Gbps or the like.

The fabric terminal FP is connected to the fabric path unit 30 and isthen connected to the fabric terminal FP of another line card via thefabric path unit 30. The fabric path unit 30 may be configured of, forexample, a fabric card having a switching function or may be configuredof a wiring board (backplane) having a full-mesh wiring. In the formercase, the fabric terminal FP is connected to the fabric card and is thenconnected to the fabric terminals FP of other line cards via theswitching of the fabric card. In the latter case, the fabric terminal FPis configured of a plurality of terminals, and the plurality ofterminals are connected to the corresponding terminals of other linecards via the full-mesh wiring provided on the backplane. In thefollowing description, the latter case is assumed.

FIG. 9 is a block diagram illustrating a configuration example of thehigh-bandwidth line card in the relay device of FIG. 8. FIG. 10A is aschematic diagram illustrating a configuration example of an LC table ofFIG. 9, FIG. 10B is a schematic diagram illustrating a configurationexample of a port table of FIG. 9, and FIG. 10C is a schematic diagramillustrating a configuration example of an FDB of FIG. 9. In FIG. 9,when a frame is received at the physical port PPh, an external interfaceunit 35 adds a reception port identifier indicating the line card andthe physical port, which have received the frame, to the frame, andtransmits it to a relay processing unit 37 or a processor unit CPU.Also, the external interface unit 35 transmits the frame from the relayprocessing unit 37 or the processor unit CPU to the physical port PPhbased on the destination port identifier.

The relay processing unit 37 includes the table processing unit 16, theVID conversion unit 17, the FDB processing unit 18 and the loopprevention unit 20. The table processing unit 16 includes the ingress LPtable 21 a and the egress LP table 21 b as the LP table 21. Each of theingress/egress LP tables 21 a and 21 b has the configuration illustratedin FIG. 3A.

When a frame is received at the physical port PPh of its own line card,the table processing unit 16 acquires the port identifier of the logicalport from the reception port identifier {PPh} and the VLAN identifierbased on the ingress LP table 21 a. Meanwhile, when a frame istransmitted from the physical port, the table processing unit 16acquires the port identifier and the VLAN identifier of the physicalport from the destination port identifier (to be the port identifier ofthe logical port) based on the egress LP table 21 b. The tableprocessing unit 16 adds the identifiers acquired in this manner to theframe.

The VID conversion unit 17 includes an ingress VID conversion table 22 aand an egress VID conversion table 22 b as the VID conversion table 22.Each of the ingress/egress VID conversion tables 22 a and 22 b has theconfiguration illustrated in FIG. 3B. When the physical port PPh of itsown line card is connected to the PB network and a frame is received atthe physical port, the VID conversion unit 17 converts the service VLANidentifier SVID into the internal VLAN identifier IVID based on theingress VID conversion table 22 a. Meanwhile, when a frame istransmitted from the physical port, the VID conversion unit 17 convertsthe internal VLAN identifier IVID into the service VLAN identifier SVIDbased on the egress VID conversion table 22 b.

Also, when the physical port PPh of its own line card is connected tothe PBB network and a frame is received at the physical port, the VIDconversion unit 17 converts the backbone VLAN identifier BVID and theservice instance identifier ISID into the internal VLAN identifier IVIDbased on the ingress VID conversion table 22 a. Meanwhile, when a frameis transmitted from the physical port, the VID conversion unit 17converts the internal VLAN identifier IVID into the backbone VLANidentifier BVID and the service instance identifier ISID based on theegress VID conversion table 22 b. The VID conversion unit 17 adds theidentifiers converted in this manner to the frame.

When a frame is received at the physical port PPh of its own line card,the FDB processing unit 18 performs the learning of the FDB and theretrieval of the destination of the frame based on the FDB.Specifically, in the learning of the FDB, the FDB processing unit 18learns a source MAC address contained in the received frame and theinternal VLAN identifier IVID converted by the VID conversion unit 17 inassociation with the port identifier of the logical port acquired by thetable processing unit 16 to the FDB as illustrated in FIG. 10C.

At this time, in detail, when the received frame is an encapsulatedframe based on the IEEE802.1ah (that is, when the physical port PPh ofits own line card is connected to the PBB network), the FDB processingunit 18 learns the source customer MAC address CMAC and the sourceencapsulation MAC address BMAC as the source MAC addresses. On the otherhand, when the received frame is a non-encapsulated frame based on theIEEE802.1ad (that is, when the physical port PPh of its own line card isconnected to the PB network), the FDB processing unit 18 learns thesource customer MAC address CMAC as the source MAC address.

Also, at the time of the retrieval of the destination based on the FDB,the FDB processing unit 18 retrieves the FDB with using the destinationMAC address contained in the received frame and the internal VLANidentifier IVID converted by the VID conversion unit 17 as retrievalkeys. At this time, in detail, when the received frame is anencapsulated frame and the destination encapsulation MAC address BMAC isdestined for its own device, the FDB processing unit 18 retrieves theFDB with using the destination customer MAC address CMAC and theinternal VLAN identifier IVID as retrieval keys, thereby acquiring thedestination port identifier.

Further, when the received frame is an encapsulated frame and thedestination encapsulation MAC address BMAC is destined for anotherdevice, the FDB processing unit 18 retrieves the FDB with using thedestination encapsulation MAC address BMAC and the internal VLANidentifier IVID as retrieval keys, thereby acquiring the destinationport identifier. Meanwhile, when the received frame is anon-encapsulated frame, the FDB processing unit 18 retrieves the FDBwith using the destination customer MAC address CMAC and the internalVLAN identifier IVID as retrieval keys, thereby acquiring thedestination port identifier or the destination encapsulation MAC addressBMAC in addition to the destination port identifier.

The FDB processing unit 18 adds the destination port identifier (or thedestination encapsulation MAC address BMAC in addition to thedestination port identifier) acquired by the retrieval result like thisto the received frame and transmits the frame to the internal interfaceunit 36. At this time, when the retrieval result is mishit (includingthe case where the destination MAC address is MCA), the FDB processingunit 18 adds an MC flag to the received frame. When a frame is receivedfrom the internal interface unit 36, the loop prevention unit 20determines whether the relay of the received frame is the frame relaybetween the plurality of logical ports set for the physical port PPh ofits own line card, and prohibits the relay of the frame whencorresponding to it.

The internal interface unit 36 includes the MC processing unit 19 and anLC table 23 a and a port table 23 b as the MC table 23. When a frame towhich the MC flag is not added is received from the relay processingunit 37, the internal interface unit 36 directly transmits the frame tothe fabric terminal FP. Meanwhile, when a frame to which the MC flag isadded is received from the relay processing unit 37, the internalinterface unit 36 performs the multicast relay by the use of the MCprocessing unit 19.

As illustrated in FIG. 10A, the LC table 23 a retains the correspondencerelation between the internal VLAN identifier IVID and one or aplurality of line card identifiers. As illustrated in FIG. 10B, the porttable 23 b retains the correspondence relation between the internal VLANidentifier IVID and one or a plurality of logical portidentifiers/physical port identifiers. The one or plurality of logicalport identifiers/physical port identifiers are determined within a rangeof the ports provided in its own line card. For example, since the linecard LCh illustrated in FIG. 9 is provided with only one physical portPPh for which the logical port is set, only one or a plurality oflogical port identifiers are retained in FIG. 10B.

When a frame to which the MC flag is added is received, the MCprocessing unit 19 determines one or a plurality of destination linecards based on the LC table 23 a, replicates the frames by the number ofdestinations, adds the destination line card identifiers to therespective replicated frames, and then transmits the frames to thefabric terminal FP. At this time, when the frame whose destination linecard is its own line card is generated, the MC processing unit 19performs the process based on the port table 23 b.

Also, when the frame to which the MC flag is added is received at thefabric terminal FP or when the frame whose destination line card is itsown line card is generated as described above, the MC processing unit 19determines one or a plurality of destination ports based on the porttable 23 b. Then, the MC processing unit 19 replicates frames by thenumber of destinations, adds the destination port identifiers to therespective replicated frames, and then transmits the frames to the relayprocessing unit 37.

The processor CPU executes the program stored in the RAM, therebyperforming, for example, the management of its own line card and thecomplicated protocol processes in cooperation with the relay processingunit 37. Note that the external interface unit 35 and the internalinterface unit 36 are mounted in, for example, ASIC (ApplicationSpecific Integrated Circuit) or the like. In addition, the relayprocessing unit 37 is mounted in, for example, FPGA (Field ProgrammableGate Array) including an integrated RAM or the like, and the FDB ismounted in, for example, CAM (Content Addressable Memory) or the like. Aspecific mounting form of each unit is not limited thereto, and eachunit may be mounted by hardware, software, or the combination thereof asneeded.

<<Frame Relay Operation in Relay Device>>

FIG. 11 is an explanatory diagram illustrating a schematic operationexample in the case where the relay device of FIG. 8 is applied to therelay system of FIG. 5. FIG. 11 illustrates the operation example of therelay device SW1 in FIG. 5. In FIG. 11, first, the line card LCh2receives the frame (non-encapsulated frame) MCFn1 from the terminal TM1at the physical port PPh2. The frame MCFn1 contains the source MACaddress (SA) “MA1”, the destination MAC address (DA) “MCA” and theservice VLAN identifier “SVID1”. In detail, the source MAC address andthe destination MAC address are the source customer MAC address (CSA)and the destination customer MAC address (CDA).

The external interface unit 35 adds the reception port identifier {PPh2}to the received frame and then transmits it to the relay processing unit37. In the relay processing unit 37, the table processing unit 16acquires the port identifier {LP2_1} of the logical port LP2_1 from thereception port identifier {PPh2} and the service VLAN identifier “SVID1”based on the ingress LP table 21 a, and replaces the reception portidentifier with the port identifier {LP2_1}. The VID conversion unit 17converts the service VLAN identifier “SVID1” into the internal VLANidentifier “IVID1” based on the ingress VID conversion table 22 a, andadds the internal VLAN identifier “IVID1” to the frame.

The FDB processing unit 18 learns the source MAC address “MA1” and theinternal VLAN identifier “IVID1” of the frame in association with thereception port identifier {LP2_1} to the FDB. Also, since thedestination MAC address of the frame is “MCA”, the FDB processing unit18 adds the MC flag to the frame and transmits the frame to the internalinterface unit 36. Since the frame to which the MC flag is added isreceived, the MC processing unit 19 in the internal interface unit 36acquires the destination line card identifiers {LCh1} and {LCh2}corresponding to “IVID1” based on the LC table 23 a. The MC processingunit 19 adds the destination line card identifiers {LCh1} and {LCh2} tothe respective two replicated frames.

The MC processing unit 19 transmits the frame to which the destinationline card identifier {LCh1} is added to the fabric path unit 30.Meanwhile, since the frame to which the destination line card identifier{LCh2} is added is destined for its own line card, the MC processingunit 19 processes the frame by the use of the port table 23 b.Specifically, the MC processing unit 19 acquires the destination portidentifier {LP2_} corresponding to “IVID1” based on the port table 23 b.Here, since the reception port identifier and the destination portidentifier are both {LP2_1}, the MC processing unit 19 discards theframe.

The fabric path unit 30 (full-mesh wiring) relays the frame to which theline card identifier {LCh1} is added to the line card LCh1. The framerelayed to the line card LCh1 is received by the internal interface unit36 of the line card LCh1. Since the frame to which the MC flag is addedis received at the fabric terminal FP, the MC processing unit 19 of theinternal interface unit 36 acquires the destination port identifiers{LP1_1} and {LP1_2} corresponding to “IVID1” based on the port table 23b. Since the destination port identifiers are both different from thereception port identifier, the MC processing unit 19 replicates twoframes, adds the destination port identifiers {LP1_1} and {LP1_2} to therespective two frames, and transmits the frames to the relay processingunit 37.

Since the received two frames do not correspond to the relay betweenlogical ports set for the physical port PPh1 of its own line card, theloop prevention unit 20 of the relay processing unit 37 permits therelay of the two frames. Specifically, the loop prevention unit 20determines that the frame does not correspond to the relay betweenlogical ports from the fact that the reception port identifier is not{LP1_x} (x is an arbitrary integer).

The VID conversion unit 17 converts the internal VLAN identifiers“IVID1” contained in the two frames into the backbone VLAN identifier“BVID1” and the service instance identifier “ISID1” based on the egressVID conversion table 22 b. In more detail, the relay processing unit 37includes an encapsulation executing unit. The encapsulation executingunit encapsulates the two frames with the backbone VLAN identifier“BVID1”, the service instance identifier “ISID1” and thesource/destination encapsulation MAC address BMAC, thereby generatingthe encapsulated frames. The source encapsulation MAC address (BSA) is aMAC address of the relay device SW1, and the destination encapsulationMAC address (BDA) is “MCA”.

The table processing unit 16 receives the frame to which the destinationport identifier {LP1_1} is added, and acquires the port identifier{PPh1} and the backbone VLAN identifier “BVID1” of the physical portPPh1 from the destination port identifier {LP1_1} based on the egress LPtable 21 b. The table processing unit 16 replaces the destination portidentifier with the port identifier {PPh1} and further replaces thebackbone VLAN identifier of the encapsulated frame with “BVID1” (in thiscase, however, nothing is changed before and after the replacement).

Similarly, the table processing unit 16 receives the frame to which thedestination port identifier {LP1_2} is added, and acquires the portidentifier {PPh1} and the backbone VLAN identifier “BVID2” of thephysical port PPh1 from the destination port identifier {LP1_2} based onthe egress LP table 21 b. The table processing unit 16 replaces thedestination port identifier with the port identifier {PPh1} and furtherreplaces the backbone VLAN identifier of the encapsulated frame with“BVID2”.

The external interface unit 35 deletes unnecessary information added tothe frames, and then transmits the two frames (encapsulated frames)MCFc1 and MCFc2 from the physical port PPh1 based on the destinationport identifier. The encapsulated frame MCFc1 contains the source MACaddress (SA) “MA1”, the destination MAC address (DA) “MCA”, the backboneVLAN identifier “BVID1” and the service instance identifier “ISID1”.

In detail, the source MAC address (SA) contains “MA1” to be the sourcecustomer MAC address (CSA) and the MAC address of the relay device SW1to be the source encapsulation MAC address (BSA). Also, the destinationMAC address (DA) contains the destination customer MAC address (CDA) andthe destination encapsulation MAC address (BDA) to be “MCA”. Inaddition, the encapsulated frame MCFc2 is the same as the encapsulatedframe MCFc1 except that the backbone VLAN identifier BVID is different.

FIG. 12 is an explanatory diagram illustrating another schematicoperation example in the case where the relay device of FIG. 8 isapplied to the relay system of FIG. 5. FIG. 12 illustrates the operationexample of the relay device SW2 in FIG. 5. In FIG. 12, first, the linecard LCh1 receives the frame (encapsulated frame) MCFc1 from the relaydevice SW1 described with reference to FIG. 11 at the physical portPPh1.

The external interface unit 35 adds the reception port identifier {PPh1}to the received frame and then transmits it to the relay processing unit37. In the relay processing unit 37, the table processing unit 16acquires the port identifier {LP1_} of the logical, port LP1_1 from thereception port identifier {PPh1} and the backbone VLAN identifier“BVID1” based on the ingress LP table 21 a, and replaces the receptionport identifier with the port identifier {LP1_1}. The VID conversionunit 17 converts the backbone VLAN identifier “BVID1” and the serviceinstance identifier “ISID1” into the internal VLAN identifier “IVID1”based on the ingress VID conversion table 22 a, and adds them to theframe.

The FDB processing unit 18 learns the source MAC address “MA1” and theinternal VLAN identifier “IVID1” of the frame in association with thereception port identifier {LP1_1} to the FDB. In detail, the FDBprocessing unit 18 learns “MA1” to be the source customer MAC address(CSA) and the MAC address BMAC of the relay device SW1 to be the sourceencapsulation MAC address (BSA) as the source MAC addresses.

Also, since the destination MAC address of the frame is “MCA”, the FDBprocessing unit 18 adds the MC flag to the frame and transmits the frameto the internal interface unit 36. Since the frame to which the MC flagis added is received, the MC processing unit 19 in the internalinterface unit 36 acquires the destination line card identifiers {LCh1}and {LCh2} corresponding to “IVID1” based on the LC table 23 a. The MCprocessing unit 19 adds the destination line card identifiers {LCh1} and{LCh2} to the respective two replicated frames.

The MC processing unit 19 transmits the frame to which the destinationline card identifier {LCh2} is added to the fabric path unit 30.Meanwhile, since the frame to which the destination line card identifier{LCh1} is added is destined for its own line card, the MC processingunit 19 processes the frame by the use of the port table 23 b.Specifically, the MC processing unit 19 acquires the destination portidentifiers {LP1_1} and {LP1_2} corresponding to “IVID1” based on theport table 23 b.

Here, since the reception port identifier {LP1_1} is the same as thereception port identifier, the MC processing unit 19 eliminates it fromthe destination port. As a result, the MC processing unit 19 transmitsthe frame to which the destination port identifier {LP1_2} is added tothe relay processing unit 37. Since the received frame corresponds tothe relay between logical ports set for the physical port PPh1 of itsown line card, the loop prevention unit 20 in the relay processing unit37 prohibits the relay of the frame (for example, discards the frame).Specifically, the loop prevention unit 20 determines the relay betweenlogical ports from the fact that the reception port identifier is{LP1_x}(x is an arbitrary integer).

Meanwhile, the frame relayed to the line card LCh2 via the fabric pathunit 30 is received by the internal interface unit 36 of the line cardLCh2. Since the frame to which the MC flag is added is received at thefabric terminal FP, the MC processing unit 19 of the internal interfaceunit 36 acquires the destination port identifier {LP2_1} correspondingto “IVID1” based on the port table 23 b. Since the destination portidentifier is different from the reception port identifier, the MCprocessing unit 19 adds the destination port identifier {LP2_1} to theframe and then transmits the frame to the relay processing unit 37.

Since the received frame does not correspond to the relay betweenlogical ports set for the physical port PPh2 of its own line card, theloop prevention unit 20 in the relay processing unit 37 permits therelay of the frame. Specifically, the loop prevention unit 20 determinesthat the frame does not correspond to the relay between logical portsfrom the fact that the reception port identifier is not {LP2_x} (x is anarbitrary integer).

The VID conversion unit 17 converts the internal VLAN identifier “IVID1”contained in the frame into the service VLAN identifier “SVID2” based onthe egress VID conversion table 22 b. In more detail, the relayprocessing unit 37 includes a decapsulation executing unit. Thedecapsulation executing unit deletes the encapsulation portion of theframe (encapsulated frame) to generate a non-encapsulated framecontaining the service VLAN identifier “SVID2”.

The table processing unit 16 receives the frame to which the destinationport identifier {LP2_1} is added, and then acquires the port identifier{PPh2} and the service VLAN identifier “SVID2” of the physical port PPh2from the destination port identifier {LP2_1} based on the egress LPtable 21 b. The table processing unit 16 replaces the destination portidentifier with the port identifier {PPh2} and further replaces theservice VLAN identifier of the non-encapsulated frame with “SVID2” (inthis case, however, nothing is changed before and after thereplacement).

The external interface unit 35 deletes unnecessary information added tothe frame, and then transmits the frame (non-encapsulated frame) MCFn2from the physical port PPh2 based on the destination port identifier.The non-encapsulated frame MCFn2 contains the source MAC address (SA)(in other words, source customer MAC address (CSA)) “MA1”, thedestination MAC address (DA) (in other words, destination customer MACaddress (CDA)) “MCA” and the service VLAN identifier “SVID2”.

In FIG. 11 and FIG. 12, in the learning of the FDB, in order tosynchronize the contents retained in the FDBs of the respective linecards, for example, the learning frame containing only a header portionof the received frame is used. In the example of FIG. 11, the relayprocessing unit 37 of the line card LCh2 generates the learning frameand transmits it to all the line cards except its own line card. Therelay processing unit 37 of each line card which has received thelearning frame learns the source information contained in the learningframe to the FDB of its own line card.

In addition, the low-bandwidth line card LC11 illustrated in FIG. 8 doesnot include the table processing unit 16 and the loop prevention unit 20of FIG. 9, and is configured to perform the same process as that in FIG.11 and others based on the port identifier of a physical port instead ofthat of a logical port. For example, the FDB processing unit 18 in theline card LC11 learns the MAC address and the internal VLAN identifierIVID in association with the port identifier of the physical port (forexample, {PP11}) to the FDB. Accordingly, as illustrated in FIG. 10C,the port identifier of a logical port and the port identifier of aphysical port are present in a mixed manner in the FDB in each linecard. However, the FDB processing unit 18 in each line card can handlethe port identifier of a physical port and the port identifier of alogical port without particularly discriminating them. Thus, thesimplification of the process can be achieved.

As described above, by using the relay device according to the secondembodiment, various advantages described in the first embodiment can beobtained in the efficient mechanism using the chassis-type L2 switch.For example, by making the loop prevention unit 20 function in the linecard on the egress side, the loop can be efficiently prevented.

In the foregoing, the invention made by the inventors of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention. For example, theembodiments above have been described in detail so as to make thepresent invention easily understood, and the present invention is notlimited to the embodiment having all of the described constituentelements. Also, a part of the configuration of one embodiment may bereplaced with the configuration of another embodiment, and theconfiguration of one embodiment may be added to the configuration ofanother embodiment. Furthermore, another configuration may be added to apart of the configuration of each embodiment, and a part of theconfiguration of each embodiment may be eliminated or replaced withanother configuration.

For example, the relay system in which the PBB network 11 is used andthe path is selected by the backbone VLAN identifier BVID has been takenas an example, but it is not always necessary to use the PBB network 11,and the relay system in which the path is selected by the use of ageneral VLAN identifier is also applicable. In addition, although an L2switch is taken as an example of the relay device here, a layer 3 (L3)switch for performing an L3 processing in addition to the L2 processingof the OSI reference model is also applicable.

What is claimed is:
 1. A relay device comprising: a physical port; alogical port table which retains a combination of the physical port anda VLAN identifier in association with a logical port; a table processingunit which acquires the logical port based on the logical port tablewhen a frame is received at the physical port; an FDB (ForwardingDataBase); an FDB processing unit which learns a source MAC addresscontained in the received frame in association with the logical portacquired by the table processing unit to the FDB; a loop preventionunit; a VID conversion unit which converts a VLAN identifier containedin the received frame into an internal VLAN identifier; and a multicastprocessing unit which retains a correspondence relation between theinternal VLAN identifier and the logical port or a plurality of logicalports, and determines the logical port or the plurality of logical portsto be a destination or destinations based on the internal VLANidentifier of the frame when the received frame is a multicast frame,wherein the plurality of the logical ports are set for the physical portby the logical port table, and the loop prevention unit prohibits framerelay between the plurality of logical ports set for the physical port.2. A relay device comprising: a physical port; a logical port tablewhich retains a combination of the physical port and a VLAN identifierin association with a logical port; a table processing unit whichacquires the logical port based on the logical port table when a frameis received at the physical port; an FDB (Forwarding DataBase); an FDBprocessing unit which learns a source MAC address contained in thereceived frame in association with the logical port acquired by thetable processing unit to the FDB; and a loop prevention unit, wherein aplurality of the logical ports are set for the physical port by thelogical port table, the loop prevention unit prohibits frame relaybetween the plurality of logical ports set for the physical port, thephysical part is one of a plurality of physical ports for which thelogical ports can be set, and the loop prevention unit can set whetherframe relay between the plurality of logical ports is prohibited foreach of the plurality of physical ports.
 3. A relay system comprising aplurality of relay devices connected via communication lines, wherein afirst relay device which is at least one of the plurality of relaydevices includes: a physical port connected to other relay devices viathe communication lines; a logical port table which retains acombination of the physical port and a VLAN identifier in associationwith a logical port; a table processing unit which acquires the logicalport based on the logical port table when a frame is received at thephysical port; an FDB (Forwarding DataBase); an FDB processing unitwhich learns a source MAC address contained in the received frame inassociation with the logical port acquired by the table processing unitto the FDB; and a loop prevention unit, wherein a plurality of thelogical ports are set for the physical port by the logical port table,the loop prevention unit prohibits frame relay between the plurality oflogical ports set for the physical port, the physical port of the firstrelay device is connected to at least a second relay device and a thirdrelay device, the second relay device is connected to the third relaydevice without interposing the first relay device, the logical porttable of the first relay device retains two of the logical portsconnected to the second relay device and the third relay device, and theloop prevention unit of the first relay device prohibits frame relaybetween the two logical ports.
 4. The relay system according to claim 3,wherein the first relay device further includes: a VID conversion unitwhich converts a VLAN identifier contained in the received frame into aninternal VLAN identifier; and a multicast processing unit which retainsa correspondence relation between the internal VLAN identifier and thelogical port or the plurality of the logical ports, and determines atleast one of the logical ports to be a destination based on the internalVLAN identifier when the received frame is a multicast frame.
 5. Therelay system according to claim 4, wherein the same internal VLANidentifier is set to the two of the logical ports connected to thesecond relay device and the third relay device.